First of all, i'm no expert in this. If you need to develop for portal, use portlets. If you don't, then use servlets/jsps. I don't think you can compare them this way since they are, at least in my understanding, two different things.
But I think using portals or "normal" web application depends a lot on personal taste and the kind of application you want to provide. I'm sure that both, portlets and JSP/servlets, technically have advantages and disadvantages like most technologies, so I'd say you can't simply tell which one is better for general usage.
My personal experience is that it depends on the content of a website which one I personally would prefer. For example in iGoogle it's nice that you can easily combine and move all kinds of gadgets ranching from a weather forecast to a calculator. In contrast on a website with more informative content like a technical article for example I find it more disturbing to have lots of gadgets and windows with bells and whistles all over the page. This is of course only my personal opinion.
I understand that it’s a matter of personal taste or requirements, but as I see the web applications nowadays of how you do things or maintain applications, pages, and other cool stuffs, development wise, developers were extending other components beyond the “normal” web applications.
Now, one technology I am sitting is JSR 286, rather than comparing it w/ other technology, maybe we can talk about its advantages, challenges or experiences using it in your development.
Now we have a problem because we would most probably need a portal expert for this discussion
My understanding of the basics of portal technology is that it's easy to combine basic building blocks to more complex web applications. This seams like a very component oriented approach which is usually a good thing to make applications or parts of more reusable and maintainable by focusing on this modular application design.
Unfortunately I don't know very much details what's exactly going on behind the scenes or what advantages it may give you during development, so I guess I can't give you a more reasonable answert. But I'm user others here can...
I have only just started using the Liferay framework that is built on top of the portal/portlet concept.
One Major and sometimes decision-making disadvantage is the non-asynchronous processing of page actions that cause all portlets of a page to re-render. Although ajax is possible, This is not what the basic portal pattern promotes, leading to a somewhat slow user experience.
Seems this thread has been awaken once more. You've mentioned a lot of good points out there, most especially when it comes to composing each applications/portlet for the portal.
The separation of views or pages per web application in a portal can really be a great deal (+1 points) for Portal/Porlet Development.
Although, I am not pretty much sure about the slowness, perhaps that can be resolved during performance testing and tuning phases.
Another side I am looking at would be the time-to-market (or hosting) the application, if the application is for public consumptions, there are few hosting companies out there that offer good services when it comes to java hosting.
They are at most only offering tomcat container for deploying your web applications, and I am not sure if there are good hosting companies or service out there that can cater for Portal/Portlet deployment.
I am mentioning this area for Portal/Portlet Development since some how if we development a good applications out of it, but we cannot get it out of the market (if we are operating by our selves for example), then it is a problem.
But if some corporations will do this deployment for you or you are working for company that is doing Portal/Portlet Development then its fine.
What is that? Is that a mongol hoarde? Can we fend them off with this tiny ad?